You've probably noticed those container ships plowing through Pacific blue waters to transport cars, books, wood and other products that we use in our everyday lives. Sometimes they share the ocean surface with the migrating paths of whales.

When the hard shell of a fast moving container ship meets the softer body of a migrating whale, the latter has little chance of emerging from the accident without being killed or injured. And when a 55,000-ton vessel moving at up to 24 mph hits a 55-ton whale, the ship's crew may not even know a collision occurred. These ships take about 2,000 trips per year in shipping lanes 20 miles to 50 miles off the stretch of coastline between Los Angeles and San Francisco.

Gray whales migrate between coastal lagoons in Baja California where they breed and areas of rich feeding off Alaska while humpback whales move between the continental coast and the Hawaiian and other Pacific islands. Blue and fin whales also spend time off California. Eighteen months ago a group of sperm whales, rarely seen in the region, were located off San Diego and near Santa Catalina Island.

While populations of some whale species have been recovering over the last few years, they're still a fraction of the historic levels they enjoyed before hunting decimated them. The National Oceanic and Atmospheric Administration's Fisheries Service and Office of National Marine Sanctuaries are charged with protecting whales nationwide under the Marine Mammal Protection Act, National Marine Sanctuaries Act and Endangered Species Act.

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There are compelling reasons to minimize the threats that can further reduce their numbers.

A recent Thank You Ocean Report podcast described an effort to reduce the number of "ship strikes" while allowing vital commercial traffic to continue offshore. NOAA's Office of National Marine Sanctuaries, which operates the Monterey Bay, Cordell Bank, Gulf of the Farallones and Channel Islands sanctuaries off California, began to coordinate the work after four dead blue whales were found on beaches in Santa Barbara and Ventura counties in 2007 and a subsequent investigation found they were killed as a result of collisions with ships.

In subsequent years, the deaths of five more whales were linked to ship collisions although the actual numbers of deaths and injuries are likely to be much higher, because ship-struck whales sink or drift out of public view.

Sean Hastings has been resource protection coordinator for the Channel Islands National Marine Sanctuary for the last 14 years. He and his NOAA colleagues have been leading the effort by making use of two strategies. First, they have been working with the International Maritime Organization to move shipping lanes away from areas frequented by whales.

They persuaded the agency to move the lanes in the Santa Barbara Channel away from historic concentrations of feeding blue and humpback whales. The new lanes are expected to go into effect in the summer of 2013. Hastings says that similar shipping lane adjustments will also take place on the approach to San Francisco Bay.

The second strategy is to slow the ships down, which has proven more difficult given the market pressure to move goods quickly. Hastings has proposed that the California Air Resources Board use its recently-approved cap and trade rules to allow container ships to be compensated for slowing down. "Slowing ships off the California coast significantly reduces emissions of greenhouse gases and other pollutants, as well as, reduces ship noise, fuel costs and public health impacts," he said. "Slower ships are also safer ships for endangered whales. To accomplish this we propose that monetary incentives be provided from the state's cap and trade auction proceeds to compensate for any additional ship costs incurred."

Reducing ship strikes as a cause of whale fatalities and injuries is just one component of the larger effort to keep whale populations as stable as possible -- one more way that humans and whales can co-exist.